import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;



/**
 * Created with IntelliJ IDEA.
 * Description:UDP版本的回显服务器
 * Author: WJW
 * Date: 2024-08-22
 * Time: 16:58
 */

public class UdpEchoServer {

    private DatagramSocket socket = null;

    public UdpEchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }

    //服务器的启动
    public void start() throws IOException {
        System.out.println("服务器启动！");
        while(true){
            //每次循环，就是处理一个请求到响应的过程
            //1.读取请求并解析
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
            //读到的字节数组，转成String方便后续的逻辑处理
            String request = new String(requestPacket.getData(),0,requestPacket.getLength());
            //2.根据请求计算响应（对于回显服务器来说，这一步啥都不用做）
            String response = process(request);
            //3.把响应返回到客户端
            //构造一个DatagramPacket作为响应对象
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),response.getBytes().length,
                    requestPacket.getSocketAddress());
            socket.send(responsePacket);

            //打印日志
            System.out.printf("[%s:%d] rep:%s,resp:%s\n",
                    requestPacket.getAddress().toString(),
                    requestPacket.getPort(),request,response );
        }
    }

    public String process(String request) {
       return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server = new UdpEchoServer(9090);
        server.start();
    }
}
